the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Dec 2022
Pseudo-random modulation continuous wave narrowband sodium temperature/wind lidar
Abstract. We report the first Pseudo-random Modulation Continuous Wave (PMCW) narrowband sodium temperature/wind lidar developed at the University of Science and Technology of China (USTC). The laser system uses an 1178 nm diode seed-laser and a fiber Raman amplifier with a fiber-coupled Acoustic Optical Modulator (AOM) to generate a narrowband 589.158 nm light with a power output of 1.5 W at v0, v+ and v_ frequencies. Based on an innovative technique and algorithm, the main beam and the residual beam modulated by Electro-Optic Modulator (EOM) with M-code are separately directed to the vertical and eastward directions. The 3-frequency light is designed in timing with the multiple-period 127-bit M-code groups. The uncertainties of the temperature and wind with the vertical and temporal resolutions of 1 km and 30 min/1 hr under the clear-sky condition are estimated to be 5.0 K and 10 m/s, respectively at the sodium peak. The temperature and wind results are in good agreement with those observed by satellite and nearby ground-based meteor radar, demonstrating the reliability of the PMCW narrowband sodium lidar system for measuring mesopause region temperature and wind.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(1633 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1387', Bifford Williams, 30 Jan 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
1. The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
2. In the Introduction, the authors mention useing this smaller laser for space observations. What is the effect of of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
3. Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
4. Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
5. Have you sent any of the output yellow beam (before the EOM) into the Dopper Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
6. For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
7. Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Citation: https://doi.org/10.5194/egusphere-2022-1387-RC1 -
AC1: 'Reply on RC1', Xin Fang, 11 Mar 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
- The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
Response: Thanks for your suggestion.
- In the Introduction, the authors mention using this smaller laser for space observations. What is the effect of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
Response: For space observations, the large ground backscatter signal should be considered in the design of the PMCW lidar. Our preliminary idea will be to set the beam emitting in a direction tangent to the surface to avoid the large ground backscatter signal.
- Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
Response: The 0 and 1 levels of the EOM in our lidar are about 10% and 90% respectively. The code impurity affects the results a little. But in our system, the timing is specially designed with zero-set 127 M codes after the M code sequences. Our lidar system also receives zero-code signals. Therefore, we can reduce the impact of code impurity to a certain extent.
- Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
Response: Thanks for your advice. We have modified it. About the PPLN, we described its function as the SHG in the text.
- Have you sent any of the output yellow beam (before the EOM) into the Doppler Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
Response: That’s a good question. Our co-developer from Shanghai Frequency Calibration Co., LTD. told us that the fiber amplifier had few frequency offsets and only about a few hundred of kHz frequency broadening. But we will check them in the future.
- For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
Response: That’s right. Vertical wind generally does not exceed 1-2 m/s at 1km/1hour resolution. Since our PMCW lidar has a power of only 1.5W at 589nm, the wind measurement error due to signal statistical noise is up to about 10m/s at the sodium layer peak with vertical and temporal resolutions of 1 km and 1hr. But the error of nightly mean vertical wind decreases to 3m/s at the sodium layer peak. Here we show the nightly mean vertical wind in the reasonable range just to demonstrate the PMCW lidar system working well.
- Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC1 -
AC3: 'Reply on RC1', Xin Fang, 11 Mar 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
- The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
Response: Thanks for your suggestion.
- In the Introduction, the authors mention using this smaller laser for space observations. What is the effect of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
Response: For space observations, the large ground backscatter signal should be considered in the design of the PMCW lidar. Our preliminary idea will be to set the beam emitting in a direction tangent to the surface to avoid the large ground backscatter signal.
- Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
Response: The 0 and 1 levels of the EOM in our lidar are about 10% and 90% respectively. The code impurity affects the results a little. But in our system, the timing is specially designed with zero-set 127 M codes after the M code sequences. Our lidar system also receives zero-code signals. Therefore, we can reduce the impact of code impurity to a certain extent.
- Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
Response: Thanks for your advice. We have modified it. About the PPLN, we described its function as the SHG in the text.
- Have you sent any of the output yellow beam (before the EOM) into the Doppler Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
Response: That’s a good question. Our co-developer from Shanghai Frequency Calibration Co., LTD. told us that the fiber amplifier had few frequency offsets and only about a few hundred of kHz frequency broadening. But we will check them in the future.
- For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
Response: That’s right. Vertical wind generally does not exceed 1-2 m/s at 1km/1hour resolution. Since our PMCW lidar has a power of only 1.5W at 589nm, the wind measurement error due to signal statistical noise is up to about 10m/s at the sodium layer peak with vertical and temporal resolutions of 1 km and 1hr. But the error of nightly mean vertical wind decreases to 3m/s at the sodium layer peak. Here we show the nightly mean vertical wind in the reasonable range just to demonstrate the PMCW lidar system working well.
- Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC3 -
AC4: 'Reply on AC3', Xin Fang, 11 Mar 2023
This is a repeated response, please cancel it.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC4
-
AC1: 'Reply on RC1', Xin Fang, 11 Mar 2023
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RC2: 'Comment on egusphere-2022-1387', Anonymous Referee #2, 28 Feb 2023
The paper presents a major upgrade and breakthrough of the USTC PMCW Na lidar. With current capability of measuring the MLT temperature and winds, this new type of Na lidar would have great potential for future spaceborne and airborne Na Doppler lidar missions. The lidar data presented in the paper have demonstrated the credibility of this new lidar technique. I will add that, in addition to the advantages listed in the paper, the so-called “chirp” issue imbedded in the pulsed lidar system (Yuan et al., 2009) is not an issue for PMCW system, because of its “pure” spectrum. My recommendation is to publish after the corrections of some minor technical issues.
Line 75, “term the transmitted light the main light, and the reflected output light the residual light”
Line 77, “To improve the overall efficiency of the lidar,… for the residual light detection… and achieving the complete…”
Line 143, “we send the lidar laser beam at a distance…”
Line 150, delete “to receive the backscattered returned signals”
Line 201, “the temperature results within are…”
Line 209, is the SABER temperature profile an instantaneous sample at the lidar station or an averaged one over an area? If it is the later, please specify the latitudinal and longitudinal range.
Line 225, “in good agreement”,
Line 238, what is the uncertainty of the MWR wind measurement?
Line 244, “demonstrates good agreement …”
Citation: https://doi.org/10.5194/egusphere-2022-1387-RC2 -
AC2: 'Reply on RC2', Xin Fang, 11 Mar 2023
The paper presents a major upgrade and breakthrough of the USTC PMCW Na lidar. With current capability of measuring the MLT temperature and winds, this new type of Na lidar would have great potential for future spaceborne and airborne Na Doppler lidar missions. The lidar data presented in the paper have demonstrated the credibility of this new lidar technique. I will add that, in addition to the advantages listed in the paper, the so-called “chirp” issue imbedded in the pulsed lidar system (Yuan et al., 2009) is not an issue for PMCW system, because of its “pure” spectrum. My recommendation is to publish after the corrections of some minor technical issues.
Response: Thanks for your comments.
Line 75, “term the transmitted light the main light, and the reflected output light the residual light”
Response: Done.
Line 77, “To improve the overall efficiency of the lidar,… for the residual light detection… and achieving the complete…”
Response: Done.
Line 143, “we send the lidar laser beam at a distance…”
Response: Done.
Line 150, delete “to receive the backscattered returned signals”
Response: Done.
Line 201, “the temperature results within are…”
Response: Done.
Line 209, is the SABER temperature profile an instantaneous sample at the lidar station or an averaged one over an area? If it is the later, please specify the latitudinal and longitudinal range.
Response: SABER measurements temperature profile using limb remote sensing technique. It is an averaged profile over a small area. We can estimate the range from the limb geometry. At 100km tangent height, the latitudinal and longitudinal ranges are about 2º and 0.05º respectively.
Line 225, “in good agreement”,
Response: Done.
Line 238, what is the uncertainty of the MWR wind measurement?
Response: The uncertainty of the meteor radar wind for 1hr average is less than 5m/s at 86km.
Line 244, “demonstrates good agreement …”
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC2
-
AC2: 'Reply on RC2', Xin Fang, 11 Mar 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-1387', Bifford Williams, 30 Jan 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
1. The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
2. In the Introduction, the authors mention useing this smaller laser for space observations. What is the effect of of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
3. Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
4. Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
5. Have you sent any of the output yellow beam (before the EOM) into the Dopper Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
6. For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
7. Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Citation: https://doi.org/10.5194/egusphere-2022-1387-RC1 -
AC1: 'Reply on RC1', Xin Fang, 11 Mar 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
- The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
Response: Thanks for your suggestion.
- In the Introduction, the authors mention using this smaller laser for space observations. What is the effect of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
Response: For space observations, the large ground backscatter signal should be considered in the design of the PMCW lidar. Our preliminary idea will be to set the beam emitting in a direction tangent to the surface to avoid the large ground backscatter signal.
- Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
Response: The 0 and 1 levels of the EOM in our lidar are about 10% and 90% respectively. The code impurity affects the results a little. But in our system, the timing is specially designed with zero-set 127 M codes after the M code sequences. Our lidar system also receives zero-code signals. Therefore, we can reduce the impact of code impurity to a certain extent.
- Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
Response: Thanks for your advice. We have modified it. About the PPLN, we described its function as the SHG in the text.
- Have you sent any of the output yellow beam (before the EOM) into the Doppler Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
Response: That’s a good question. Our co-developer from Shanghai Frequency Calibration Co., LTD. told us that the fiber amplifier had few frequency offsets and only about a few hundred of kHz frequency broadening. But we will check them in the future.
- For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
Response: That’s right. Vertical wind generally does not exceed 1-2 m/s at 1km/1hour resolution. Since our PMCW lidar has a power of only 1.5W at 589nm, the wind measurement error due to signal statistical noise is up to about 10m/s at the sodium layer peak with vertical and temporal resolutions of 1 km and 1hr. But the error of nightly mean vertical wind decreases to 3m/s at the sodium layer peak. Here we show the nightly mean vertical wind in the reasonable range just to demonstrate the PMCW lidar system working well.
- Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC1 -
AC3: 'Reply on RC1', Xin Fang, 11 Mar 2023
This paper describes a new lidar and shows initial observations using the PMCW technique that has been discussed for years but has not been used operationally. The paper is well written and the results look good. I just have a few small comments and I do not need to see the paper again before publication unless other reviewers have significant concerns.
- The writing is generally good and understandable but it could use a read over by a native English speaker to fix some prepositions, etc.
Response: Thanks for your suggestion.
- In the Introduction, the authors mention using this smaller laser for space observations. What is the effect of the large ground backscatter signal on the PMCW method. This can't easily be avoided with a large baseline like the near-field signal in a ground-based system
Response: For space observations, the large ground backscatter signal should be considered in the design of the PMCW lidar. Our preliminary idea will be to set the beam emitting in a direction tangent to the surface to avoid the large ground backscatter signal.
- Section 2: For the EOM, what are the 0 and 1 levels? Many EOM's are 10% and 90% splitting. How does this code impurity affect the results?
Response: The 0 and 1 levels of the EOM in our lidar are about 10% and 90% respectively. The code impurity affects the results a little. But in our system, the timing is specially designed with zero-set 127 M codes after the M code sequences. Our lidar system also receives zero-code signals. Therefore, we can reduce the impact of code impurity to a certain extent.
- Section 3: Your fiber AOM is more properly described as an AO frequency shifter, since frequency shifting is the main goal. That also avoids any confusion with your EO modulator. Similarly, figures 1 and 2 use different terms for the same device: PPLN vs SHG, you might want to pick one for clarity,
Response: Thanks for your advice. We have modified it. About the PPLN, we described its function as the SHG in the text.
- Have you sent any of the output yellow beam (before the EOM) into the Doppler Free to check for frequency offsets/broadening in the 2nd fiber amplifier?
Response: That’s a good question. Our co-developer from Shanghai Frequency Calibration Co., LTD. told us that the fiber amplifier had few frequency offsets and only about a few hundred of kHz frequency broadening. But we will check them in the future.
- For Figure 7a and 8: At 1km/1hour resolution it would be very rare to see any true vertical winds of more than 1-2 m/s, based on many observations with much higher SNR Na systems. So much of the signal in Figure 7a is likely noise. How do the measured vertical winds compare with your PMCW error calculations? You should add error bars to Figure 8.
Response: That’s right. Vertical wind generally does not exceed 1-2 m/s at 1km/1hour resolution. Since our PMCW lidar has a power of only 1.5W at 589nm, the wind measurement error due to signal statistical noise is up to about 10m/s at the sodium layer peak with vertical and temporal resolutions of 1 km and 1hr. But the error of nightly mean vertical wind decreases to 3m/s at the sodium layer peak. Here we show the nightly mean vertical wind in the reasonable range just to demonstrate the PMCW lidar system working well.
- Section 5, line 260: "And the zonal wind..." -> "The zonal wind..."
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC3 -
AC4: 'Reply on AC3', Xin Fang, 11 Mar 2023
This is a repeated response, please cancel it.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC4
-
AC1: 'Reply on RC1', Xin Fang, 11 Mar 2023
-
RC2: 'Comment on egusphere-2022-1387', Anonymous Referee #2, 28 Feb 2023
The paper presents a major upgrade and breakthrough of the USTC PMCW Na lidar. With current capability of measuring the MLT temperature and winds, this new type of Na lidar would have great potential for future spaceborne and airborne Na Doppler lidar missions. The lidar data presented in the paper have demonstrated the credibility of this new lidar technique. I will add that, in addition to the advantages listed in the paper, the so-called “chirp” issue imbedded in the pulsed lidar system (Yuan et al., 2009) is not an issue for PMCW system, because of its “pure” spectrum. My recommendation is to publish after the corrections of some minor technical issues.
Line 75, “term the transmitted light the main light, and the reflected output light the residual light”
Line 77, “To improve the overall efficiency of the lidar,… for the residual light detection… and achieving the complete…”
Line 143, “we send the lidar laser beam at a distance…”
Line 150, delete “to receive the backscattered returned signals”
Line 201, “the temperature results within are…”
Line 209, is the SABER temperature profile an instantaneous sample at the lidar station or an averaged one over an area? If it is the later, please specify the latitudinal and longitudinal range.
Line 225, “in good agreement”,
Line 238, what is the uncertainty of the MWR wind measurement?
Line 244, “demonstrates good agreement …”
Citation: https://doi.org/10.5194/egusphere-2022-1387-RC2 -
AC2: 'Reply on RC2', Xin Fang, 11 Mar 2023
The paper presents a major upgrade and breakthrough of the USTC PMCW Na lidar. With current capability of measuring the MLT temperature and winds, this new type of Na lidar would have great potential for future spaceborne and airborne Na Doppler lidar missions. The lidar data presented in the paper have demonstrated the credibility of this new lidar technique. I will add that, in addition to the advantages listed in the paper, the so-called “chirp” issue imbedded in the pulsed lidar system (Yuan et al., 2009) is not an issue for PMCW system, because of its “pure” spectrum. My recommendation is to publish after the corrections of some minor technical issues.
Response: Thanks for your comments.
Line 75, “term the transmitted light the main light, and the reflected output light the residual light”
Response: Done.
Line 77, “To improve the overall efficiency of the lidar,… for the residual light detection… and achieving the complete…”
Response: Done.
Line 143, “we send the lidar laser beam at a distance…”
Response: Done.
Line 150, delete “to receive the backscattered returned signals”
Response: Done.
Line 201, “the temperature results within are…”
Response: Done.
Line 209, is the SABER temperature profile an instantaneous sample at the lidar station or an averaged one over an area? If it is the later, please specify the latitudinal and longitudinal range.
Response: SABER measurements temperature profile using limb remote sensing technique. It is an averaged profile over a small area. We can estimate the range from the limb geometry. At 100km tangent height, the latitudinal and longitudinal ranges are about 2º and 0.05º respectively.
Line 225, “in good agreement”,
Response: Done.
Line 238, what is the uncertainty of the MWR wind measurement?
Response: The uncertainty of the meteor radar wind for 1hr average is less than 5m/s at 86km.
Line 244, “demonstrates good agreement …”
Response: Done.
Citation: https://doi.org/10.5194/egusphere-2022-1387-AC2
-
AC2: 'Reply on RC2', Xin Fang, 11 Mar 2023
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Xin Fang
Feng Li
Lei-lei Sun
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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